The present invention relates to a document readout device, and more particularly to a document readout device for converting information on a document to electric signals.
One recently proposed document readout device is illustrated in FIG. 5 of the accompanying drawings. An original document O bearing information to be read out is placed on a support plate 30 of glass. The document readout device includes an image-forming optical system 40, an unmagnification sensor 50, and a line illuminating unit 60. The direction normal to the sheet of FIG. 5 will hereinafter be referred to as a Z direction.
The image-forming optical system 40 comprises a roof mirror array 42, a lens array 44, and a right-angled mirror 46, and a housing 48 accommodating the roof mirror array 42, the lens array 44, and the right-angled mirror 46 in mutually spaced relationship. The roof mirror array 42 is of a structually integral optical component having an array of roof mirrors arranged at a constant pitch in the Z direction, each of the roof mirrors having a ridge extending vertically in FIG. 5. The lens array 44 includes an array of lenses arranged at the same pitch as that of the roof mirrors of the roof mirror array 42. Each of the lenses of the lens array 44 is optically associated with one of the roof mirrors of the roof mirror array 42.
Each of the lenses of the lens array 44 and the corresponding roof mirror combined therewith jointly constitute a retrodirective image-forming optical system for forming an unmagnified iamge of an object on a surface of the object. Therefore, the roof mirror array 42 and the lens array 44 jointly constitute an array of such retrodirective image-forming optical systems.
The right-angled mirror 46 comprises two plane mirrors which are elongate in the Z direction, the plane mirrors having mirror surfaces normal to each other. The roof-mirror array 42, the lens array 44, and the right-angled mirror 46 are retained in the housing 48 as shown in FIG. 5. The housing 48 has a pair of slits extending in the Z direction and aligned vertically with each other, with cover glass strips 41, 43 fitted in the respective slits.
The original document O is fed by a document feeder (not shown) in the direction of the arrow (FIG. 5) while in contact with the support plate 30. As the document O is thus fed along, a slit ray of light extending in the Z direction is applied from the light illuminating unit 60 to the document O. Light reflected from the illuminated area of the document O enters the image-forming optical system 40 through the cover glass strip 41 in the upper slit of the housing 48 and is reflected to the right by the right-angled mirror 46. Then, the light passes through the lens array 44 and is reflected by the roof mirror array 42 back through the lens array 44 to the right-angled mirror 46. The light is reflected by the right-angled mirror 46 to exit from the image-forming optical system 40 through the cover glass strip 43. The light then falls on the unmagnification sensor 50 to form an unmagnified erect image of the illuminated area of the document O. The unit magnification sensor or unmagnification sensor 50 comprises a self-scanned photosensor composed of an array of small photosensor elements arranged in the Z direction. The length for which the photosensor elements are arranged is selected to be equal to or larger than the width of the document O in the Z direction. The information on the document O can be successively read out and converted to electric signals by cyclically scanning the unmagnification sensor 50 in timed relation to the travel of the document O.
With the document readout device shown in FIG. 5, the area of the document O that is illuminated by the line illuminating unit 60 and the light detecting area on the unmagnification sensor 50 are required to be in proper image-forming relationship through the intermediary of the image-forming optical system 40. It has been tedious and time-consuming to adjust the relative positions of the line illuminating unit 60, the image-forming optical system 40, and the unmagnification sensor 50.
The photosensor of the unmagnification sensor 50 has heretofore been fabricated of an amorphous semiconductor driven by a driver circuit located outside of the unmagnification sensor 50. Leads from the individual photosensor elements are patterned on the photosensor baseboard and are relatively large in size.
Recently, there has been developed a mass-produceable unmagnifcation sensor in which driver circuits are arranged in line on a photosensor baseboard, the unmagnification sensor being of about the same size as that of the cover glass strips 41, 43 shown in FIG. 5.